Tuning device for signal-diaphragms.



F. G. WHITTINGTON.

TUNING DEVICE FOR SIGNAL DIAPHRAGNIS.

APPLICAIION mw 1AN.21. |911.

' A MITA FREDERIK Gr. WHITTINGTON, OF CHICAGO, ILLINOIS, ASSIGNOR TO STEWART-WARNER SPEEDOMETER CORPORATION, OF CHICAGO, ILLINOIS, A CORPORATION F VIRGINIA.

TUNING DEVICE FOR SIGNAL-DIAPHRAGMS. i,

Specification of Letters Patent.

Patented Mar. 25, 1919.

Application led January 27, 1917. Serial No. 144,821.

for Signal-Diaphragms, of whichl the fol` lowing is a specification', reference being had to the accompanying drawings, forming a part thereof.

This invention relates to that class of signal devices in which a diaphragm is rap-` idly vibrated by mechanical means to produce a sound and the purpose of this invention is to provide kmeans for adjusting the diaphragm to vary the pitch of the sound produced so as to secure the desired tone.

It consists of' the features and elements described and shown in the ldrawings as indicated by the claims.

In the drawings Figure l is a side elevation partly in section, showing a diaphragm signal device with tuning means applied to the diaphragm in accordance with this invention.

Fig. 2 is a detailed section showing a modified form of tuning device.

Referring first to Fig. 1, the drawing may be understood as showing a motor, 1, which y may be either an electric motor or a manually operated drivingtrain of an suitable construction, having a power sha t, 2, provided with a cam wheel, 3, having serrations, or corrugations, 3, in position to engage a wear piece, or button, 4, secured to the diaphragm, 5, approximately at its center. The rotation of the shaft, 2, causing the corrugations, 3, to successively engage the wear piece, or button, 4, produces a rapid vibration of the diaphragm, 5, resulting in a corresponding vibration of the air column in the chamber, 6, and horn, 7, which is recognized as the sound. The diaphragm, 5, as-

will be noted, is securely clamped at its periphery between the flange, 1, of the motor housing, and the fiange, 6, of the chamber, 6, cushioning washers, 8, 8, being preferably inserted between the diaphragm and these flanges respectively.

It has been customary in devices of this sort to provide for tuning the signal by adjusting the wear piece, 4, along its axis within, its mounting on the diapraghm, 5, or by adjusting the motor, 1, or at least the cam wheel, 3, along its axis, so as to vary the amount of overlap of the cam corrugations or teeth, 3, with respect to the wear button, 4. The eifectof such adjustment is to increase or diminish the resistance offered by the button, 4, to rotation of the motor shaft, 2, thus altering the frequency of the impulses transmitted to the. diaphragm, 5, since, with a given driving force for the motor, any variation in the resistance, or work imposed upon the motor, will `vary its speed.

An of the methods of adjustment just described is somewhat less convenient'than might be desired', especially the arrangement in which the wear button, 4, itself is adjusted upon the diaphragm, 5, and particularly when a rather vlong horn isfurnished, because either the screw and lock nut, provided for such/adjustment can only be reached through the long horn by means of special tools, or else the entire front chamber, 6, must be removed to render them accessible, and this amounts to disassembling the whole signal. Then the adjustment cannot be made while the motor, 1, is running and, thus, to secure a particular tone, it is necessary to make a series of trials. By the present invention theadjustin means are rendered readily accessible'wih ordinary tools and may be manipulated while the signal is being sounded, so as to vary the tone throughout its entire range, thus permitting a quick determination of the proper adjustment.

In the form shown in Fig. 1 an adjusting screw, 9, is `fitted with a flanged collar, 12, interiorly threaded to engage a portion of the screw, 9, and exteriorly threaded to receive a clamping nut, 13, between which and the flange, 12, of the collar, 12, the diaphragm, 5, is clamped witlrlsuitable cushioning washers, 14, interposed. The screw, 9, is journaled in an aperture of the flange, 1, in the' motor housing, and is secured against longitudinal movement by its own flange, 9, and a clampin nut, 9. It will be evident that rotation o? the screw, 9, will cause longitudinal travel of its threaded collar, or nut, 12, carrying with it that portion of the diaphragm, 5, which is engaged between the flange of the collar, 12, and the nut, 13. When the desired adjustment is reached, the adjusting screw, 9, may be se cured against further rotation by the clamping nut, 9*.

Fig. 2 shows a modification, consisting in that the adjusting screw, 9m, is carried in a threaded mounting in the flange, la, but positively engages the diaphragm, 5,v in both directions, being provided with a head, 9, which is drilled and threaded to receive a clamp-screw, 9, 'carrying under its head a washer, 9D, and thus securing the adjusting screw, 9m, to the diaphragm, 5, with cushioning washers, 16, however, interposed as in the other form. The protruding end of the screw is slotted at, 9?, and a lock-nut, 91, serves to retain the parts in adjusted p0- Sition. i

It will be seen that all of the forms above described can be manipulated without disturbing the mounting of the diaphragm, or without the use of special tools, and while the diaphragm is being vibrated by rotation of the cam wheel, 3, so that, as soon as the desired .tone is secured, the adjusting screw can be locked in position and the adjustment is completed. It will be'evidentthat this type of adjustment not only operates to vary the possible speed of the motor shaft, 2, but also alters the natureofthe diaphragm as a sound-producing element, in that it restricts its vibration ata point other than its confined periphery.

I claim:

1. In a signal device, in combination with a diaphragm, a mounting member to which it is -peripherally secured, and means for vibrating said diaphragm, said diaphragm being apertured at a point between said vibrating means and its peripheral securement, means extending through said aperture and clamped 'against both sides of the diaphragm together with an adjusting screw extending from said means into rotative engagement with the' mounting member, for variably stressing the diaphragm.

2. In the combination set out in claim 1, the means which is clamped in the diaphragm aperture being in the nature of a 'nut threaded to engage the adjusting screw,

and said screw being stopped against endwisemovement in the mounting member.

In testimony whereof, I have hereunto set my hand at Chicago, Illinois, this 18 day of January, 1917.

FREDER'IK G. WHI'ITINGTON. 

